1. Field of the Invention
The present invention relates to a recorder which records an image on a record medium by recording pixels of different number from the number of input pixels.
2. Description of the Prior Art
Many methods have been proposed to produce recording pixels of different number from the number of input pixels. When recording pixels of a larger number than the number of input pixels are to be produced, it is usual to obtain density data of a recording pixel between adjacent input pixels by interpolation.
Let us assume that the number of input pixels in one scan line is 480 and that it is to be increased by a factor of 4/3 by interpolation. The number of input pixels of 480 is thus increased to the number of recording pixels, of 640. As shown in FIG. 1, the 640th recording pixel b.sub.640 is located outside the input pixel a.sub.480 and density data for b.sub.640 cannot be exactly obtained.
Let us assume that the interpolation is carried out bidirectionally to record the image during forward and backward movements of a record head.
Positions b of the recording pixels by the interpolation during the forward movement are shown by .circle. and positions b' of the recording pixels during the backward movement are shown by .DELTA..
If the same interpolation is effected in both directions, the positions of the recording pixels in the forward movements and the positions of the recording pixels in the backward movement are slightly displaced from each other as shown in FIG. 1. If the data are recorded at the same positions in the scan direction, the resolution of the recorded image is lowered. If they are to be recorded at displaced positions, a complex mechanism is required for the recording unit. This leads to increase of size of apparatus and increase of cost, and the resulting image may tend to be unattractive because edges of the recorded image do not align.